To elucidate the true nature of flaccid paralysis of infant polyradiculoneuritis with Guillain-Barres syndrme (G.N.S.), which occurred intermittently in the coast regions of the Inland Sea from 1950 to 1955, the author made comparative studies on the electromyograms of this disease with those of paralytic poliomyelitis (H.M.), and obtained the following results: 1. In 23 cases with G.B.S. and 41 cases of H.M. electromyographical examinations were carried out 76 and 102 times up to 10 weeks after the onset of disease, and their tested total number of muscles came up to 884 and 716 respectively. Among them 686 muscles of G.B.S. and 510 of H.M. showed abnormal electromyographic findings. These abrormal electromyograms were classified into 6 types, namely, those at the maximum voluntary contraction: electrical silence, low amplitude NAIU voltage (L.A.NAUV.), synchronization voltage (S.V.), complex NMU voltage, and decreased spike number of normal NMU voltage; and those at rest, fibrillation voltage. The two diseses showed some differences in the percentage of each abnormal elect romyograms in these various muscles. Namely, of them the most marked difference was the L.A. NMU V. at the maximum contraction; and it was observed in 25.3 per cent of G.B.S. and in 1.1 per cent of H.M., while electrical silence was observed in 8.9 per cent of the former and in 28.6 per cent of the latter. On the other hand, synchronization voltage was noticed in 17 per cent of G.B.S. while in 12.6 per cent of H.M., showing slightly more in the former. The normal NMU voltage was cassified into three grades; the let to the third degree according to the discharge frequency, that is to say, the number of discharges 1-15(Ⅲ). 16-30(Ⅱ), and 31-50/sec(Ⅰ). Summing them up, these discharges were found in 48.4 per cent of G.B.S. while in 57.2 per cent in H.M., As for the complex NMU voltage it was found in 0.43 per cent of the former, while in 0.4 per cent of the latter; and fibrillation voltage at rest was in 1.7 per cent and 0.4 per cent respectively, showing no significant difference in either case. 2. Follow-up examinations were studied on the 20 cases with G.B.S. presenting limb paralysis at the extreme stages one to six years after the onset of disease and on the eight cases with H.M., presenting bilateral paralysis within ten weeks, at the three years after the onset. Only 28 out of 250 muscles in G.B.S. (10 Cases out of 20) showed abnormal electromyographic findings, namely, 11.2 per cent were found to be ahnormal. While 37 muscles out of 46 of H.M. examimed within 10 weeks after the onset namely, 80.4 per cent showed the abnormality. All electromyographic findings of 28 muscles from G.B.S. were of incomplete synchronization voltage, presenting a desynchronization tendency, while in H.M. 7 muscles out of 46 (15.2% ) were of electrical silence. But these 46 muscles revealed it in 50 per cent of them within 10 weeks after the onset of disease. As for the decreased number of normal NMU voltage concerned, 17 muscles (36.9% ) were positive, while within 10 weeks after the onset 40 per cent recognized. On the other hand, S.V. of H.M. was recognized in 13 muscles out of 46 (28.2% ), though within 10 weeks after the onset it was in 19. 6 per cent of 46 muscles, moreover 10 muscles out of 13 revealed complete S.V., 3. 119 muscles out of 884 from G.B.S. and 81 muscles out of 716 from H.M. tested eletromyographicaly were negative tendon reflex. But the electrical activity at the maximum voluntary contraction was recognized in 86 muscles (72.3% ) out of the total of 119 muscles in the former and 17 muscles (20.9% ) out of 81 muscles in the latter. After 8 weeks the elctrical activity in G.B.S. came out in all muscles, while on the contrary none in H.M.. The relationship between the degree range of tendon reflex and the S.V. as well as L.A. NMU voltage was examined, and S.V. was found most often in those muscles with sluggish tendon reflex in both diseases. In G.B.S. those muscles either with normal tendon reflex or without it showed more S.V. than in H.M.. L.A. NMU voltage was found much more in the muscles without tendon reflex rather than in those with normal tendon reflex. 4. In the electrical evainiuation studied up to seven weeks after the onset in 15 cases of G.B.S. in 8 cases of H.M., hardly typical reaction of degeneration could be recognized in G.B.S. but only traces of atypical reaction of degeneration, showing reduction of excitability in the majority, while in H.M. typical and atypical reaction of degeneration could still be recognized in 50 per cent of the cases after seven weeks from the onset. 5. Above mentioned results, i.e. the electromyographical change, its relation between tendon reflex and electrical excitability, show that G.B.S. consists mainly of pathologic changes in peripheral nerves and muscles and their spinal changes are slight and transient, whereas in H.M. the main pathologic changes are held in the anterior horn of the spine.